Structure of plant photosystem I−light harvesting complex I supercomplex at 2.4 Å resolution

Photosystem I (PSI) is one of the two photosystems in photosynthesis, and performs a series of electron transfer reactions leading to the reduction of ferredoxin. In higher plants, PSI is surrounded by four light-harvesting complex I (LHCI) subunits, which harvest and transfer energy efficiently to the PSI core. The crystal structure of PSI-LHCI supercomplex has been analyzed up to 2.6 Å resolution, providing much information on the arrangement of proteins and cofactors in this complicated supercomplex. Here we have optimized crystallization conditions, and analyzed the crystal structure of PSI-LHCI at 2.4 Å resolution. Our structure showed some shift of the LHCI, especially the Lhca4 subunit, away from the PSI core, suggesting the indirect connection and inefficiency of energy transfer from this Lhca subunit to the PSI core. We identified five new lipids in the structure, most of them are located in the gap region between the Lhca subunits and the PSI core. These lipid molecules may play important roles in binding of the Lhca subunits to the core, as well as in the assembly of the supercomplex. The present results thus provide novel information for the elucidation of the mechanisms for the light-energy harvesting, transfer and assembly of this supercomplex.     

Allelopathic effects of the revegetation species Juniperus sabina L. in semiarid areas of China

Landscape and Ecological Engineering - Juniperus sabina L. is a native evergreen conifer of the Mu Us Sandy Land. It has prostrating stems that can prevent sand shifting and is an important...     

Synthesis,telomerase inhibitory and anticancer activity of new 2-phenyl-4H-chromone derivatives containing 1,3,4-oxadiazole moiety

Based on previous studies, 66 2-phenyl-4H-chromone derivatives containing amide and 1,3,4-oxadiazole moieties were prepared as potential telomerase inhibitors. The results showed most of the title compounds exhibited significantly inhibitory activity on telomerase. Among them, some compounds demonstrated the most potent telomerase inhibitory activity (IC₅₀ < 1 µM), which was significantly superior to the staurosporine (IC₅₀ = 6.41 µM). In addition, clear structure–activity relationships were summarised, indicating that the substitution of the methoxy group and the position, type and number of the substituents on the phenyl ring had significant effects on telomerase activity. Among them, compound A33 showed considerable inhibition against telomerase. Flow cytometric analysis showed that compound A33 could arrest MGC-803 cell cycle at G2/M phase and induce apoptosis in a concentration-dependent way. Meanwhile, Western blotting revealed that this compound could reduce the expression of dyskerin, which is a fragment of telomerase.     

30 years of free‐air carbon dioxide enrichment (FACE): What have we learned about future crop productivity and its potential for adaptation?

Free‐air CO₂ enrichment (FACE) allows open‐air elevation of [CO₂] without altering the microclimate. Its scale uniquely supports simultaneous study from physiology and yield to soil processes and disease. In 2005 we summarized results of then 28 published observations by meta‐analysis. Subsequent studies have combined FACE with temperature, drought, ozone, and nitrogen treatments. Here, we summarize the results of now almost 250 observations, spanning 14 sites and five continents. Across 186 independent studies of 18 C₃ crops, elevation of [CO₂] by ca. 200 ppm caused a ca. 18% increase in yield under non‐stress conditions. Legumes and root crops showed a greater increase and cereals less. Nitrogen deficiency reduced the average increase to 10%, as did warming by ca. 2°C. Two conclusions of the 2005 analysis were that C₄ crops would not be more productive in elevated [CO₂], except under drought, and that yield responses of C₃ crops were diminished by nitrogen deficiency and wet conditions. Both stand the test of time. Further studies of maize and sorghum showed no yield increase, except in drought, while soybean productivity was negatively affected by early growing season wet conditions. Subsequent study showed reduced levels of nutrients, notably Zn and Fe in most crops, and lower nitrogen and protein in the seeds of non‐leguminous crops. Testing across crop germplasm revealed sufficient variation to maintain nutrient content under rising [CO₂]. A strong correlation of yield response under elevated [CO₂] to genetic yield potential in both rice and soybean was observed. Rice cultivars with the highest yield potential showed a 35% yield increase in elevated [CO₂] compared to an average of 14%. Future FACE experiments have the potential to develop cultivars and management strategies for co‐promoting sustainability and productivity under future elevated [CO₂].     

环境因子对海南岛野生兰科植物物种组成与分布格局的影响

海南岛是中国兰科植物物种丰富度较高的地区, 了解环境因子对海南岛野生兰科植物物种组成和分布格局的影响, 对于该地区野生兰科植物的保护管理和相关研究具有重要指导意义。基于海南岛野生兰科植物调查分布样方的植被类型、海拔、坡向、坡度、年平均气温、年降水量的数据, 采用典范相关分析探索了环境因子对物种组成的影响, 并计算各个环境因子对物种组成的总效应与净效应, 同时分析了6个环境因子对野生兰科植物分布格局的影响。结果表明, 所选的6个环境因子共解释了海南岛野生兰科植物组成变异的3.7%; 植被类型、海拔、年平均气温、年降水量、坡向、坡度这6个环境因子的总效应与净效应均达显著水平, 但其解释率依次减小。所选的6个环境因子对海南岛野生兰科植物的分布均有影响, 野生兰科植物在海南岛主要分布在中海拔段、5°-35°的坡度范围、阴坡与半阴坡、年平均气温较低且年降水量较高的环境, 并且于原生植被中分布最多。     

The pollination of Habenaria rhodocheila (Orchidaceae) in South China: When butterflies take sides

Habenaria is one of the largest terrestrial genera in the family Orchidaceae. Most field studies on Habenaria species with greenish–white and nocturnal scented flowers are pollinated by nocturnal hawkmoths and settling moths. However, H. rhodocheila presents reddish flowers lacking a detectable scent and fails to fit the moth pollination syndrome. We investigated the pollinators, breeding system, and functional traits of H. rhodocheila in South China and found that two diurnal swallowtail butterflies Papilio helenus and Papilio nephelus (Papilionidae) were the effective pollinators. When butterflies foraged for nectar in the spur, the pollinia became attached between the palpi. A triangular projected median rostellar lobe was found at the entrance (sinus) of the spur of H. rhodocheila. This lobe divided the spur opening into two entrances forcing butterflies to enter their proboscides through the left or right side. When the projection of median rostellar lobe was removed, the site of pollinium attachment changed to the eyes of the butterflies, leading to a higher rate of pollinium removal but lower rate of pollinium deposition. Our quartz glass cylinder choice experiment suggested that visual rather than olfactory cues provided the major stimuli for butterflies to locate these flowers. Hand pollination experiments suggested this species was self‐compatible but pollinator‐dependent. However, the proportion of seeds with large embryos produced in self‐pollinated fruits was significantly lower than in cross‐pollinated fruits, indicating a significant inbreeding depression. Unlike many other orchid species, fruit set was higher than rates of pollinium removal, indicating a high level of pollination efficiency in a species with friable pollinia. Shifts from moth to butterfly pollination in the genus Habenaria parallel other orchid lineages providing insights into the potential for pollinator‐mediated floral trait selection.     

双斑蟋营养成分分析及评价

由于具有较好的营养价值以及较高的食物转化效率,食用昆虫特别是蟋蟀受到普遍关注。在双斑蟋（Gryllus bimaculatus,GB）营养成分测定的基础上,对比家蟋（Acheta domesticus,AD）和黑蟋（Gryllus testaceus,GT）的营养及含量,分析评价了双斑蟋的使用价值。结果显示：双斑蟋水分含量71.0%、粗蛋白含量58.60%（干重）、粗脂肪含量28.90%（干重）、粗纤维含量7.23%（干重）、灰分4.93%（干重）;蛋白含量与黑蟋相当而高于家蟋,粗脂肪和灰分含量要高于家蟋和黑蟋;双斑蟋含有17种氨基酸,总氨基酸含量51.03%（干重）,必需氨基酸含量24.76%（干重）、占总氨基酸的48.3%,氨基酸含量低于其他两种蟋蟀;双斑蟋中常量元素含量最高的为钾（6 416 mg/kg,干重）、含量最低的是钙（92 mg/kg,干重）,微量元素中锌含量较高（241 mg/kg,干重）;双斑蟋油脂中不饱和脂肪酸的相对含量为65.33%,以亚油酸（37.05%）和油酸（25.86%）为主、饱和脂肪酸以棕榈酸（25.44%）和硬脂酸（8.74%）为主。双斑蟋的脂肪酸组成、含量与家蟋相近,而与黑蟋的脂肪酸组成差别较大,三种蟋蟀中含量最高的饱和脂肪酸为棕榈酸,而含量最高的不饱和酸为亚油酸。结果表明,双斑蟋的必需氨基酸组成符合FAO/WHO推荐的氨基酸构成比例的蛋白条件,具有较高的营养价值和食用价值。